The incidence of iron-deficiency in children of low socio-economic background is estimated to be approximately five percent. In these children, iron-deficiency is associated with behavioral disorders and an overall impairment of intellectual performance as monitored by a variety of cognitive tests. In adults iron deficiency results in a decrease in the activity of platelet monoamine oxidase, a major enzyme responsible for the inactivation of the biogenic amine neurotransmitters. Since alteration in the levels of amine neurotransmitters in the CNS are related to a variety of behavioral disorders, it can be suggested that a deficit of MAO activity may be responsible for the impaired behavioral and intellectual performance in iron-deficient children. Accordingly, the purpose of the present investigation was to determine if this enzyme is also decreased in platelets of iron-deficient children. Preliminary results with a small sample population indicate platelet MAO activity is, however, not statistically different in normal and iron-deficient children. These results, if substantiated with a larger sample population, suggest that altered MAO activity, most likely, is not responsible for the behavioral change, seen in iron-deficient children. In addition, urinary levels of the biogenic amines and their major metabolites will also be determined.